The present invention relates to a drainage system wherein drain water is collected from a drainage path including a small river, guided to a plurality of drainage pump facilities, and drained into a destination river. More particularly, the present invention relates to a drainage distribution amount determining method and drainage system using the method particularly suitable for a broad area drainage system in or around an urban district.
In a conventional drainage system of this type, drainage pump facilities are automatically operated while controlling the drainage amounts independently from each other so as to maintain the water level (hereinafter called an inside water level) of each pump pool or sump within a predetermined range. One type of such a conventional drainage system is described in Japanese Patent Laid-Open Publication JP-A-2-115584.
The above-described conventional technique does not consider the water level (hereinafter called an outside water level) of a destination river. Therefore, there arises a problem that the outside level at a drainage point or at the downstream of the drainage point (hereinafter collectively called a drainage point) rises to exceed the upper limit of the outside water level.
The above problem can be solved by reducing the drainage amount at the drainage pump facility exceeding the upper limit and distributing the reduced drainage amount to another drainage pump facility which has a marginal drainage amount relative to its upper limit. However, as described above, drainage pump facilities are automatically operated while controlling the drainage amounts independently from each other so as to maintain the inside water levels within a predetermined range. Therefore, such a control of distributing a drainage amount cannot be performed.